(1) Field of Invention
The present invention relates to a mechanical pencil and, more particularly, to a mechanical pencil that includes a wheel to advance the lead disposed within the mechanical pencil.
(2) Description of Related Art
Mechanical pencils have long been known in the art. A multitude of barrel-shaped mechanical pencils have been devised that include an actuation means, where upon actuation, lead disposed within the pencil is advanced beyond an end of the barrel, thereby allowing a user to control the amount of lead being exposed to write upon a surface. By way of example, mechanical pencils have typically been formed using three types of mechanisms, a side-knock mechanism, a push-button mechanism, and a rotary-knock mechanism.
Side-knock mechanical pencils typically include a barrel having an opening in a side wall. A knock lever is mounted within the opening and pivotally mounted with respect to the barrel. The knock lever is connected with a chuck mechanism such that by depressing the lever, the chuck mechanism is opened to allow advancement of a piece of lead. A problem associated with such a pencil is that depressing the lever advances the lead in step-like equal increments, preventing a user from rolling the lead out in a smooth fashion.
Push-button mechanical pencils suffer from many of the same setbacks as side-knock mechanical pencils. Push-button pencils typically comprise a barrel with a push-button opposite a tip end. The push-button is connected with a lead chamber such that pressing the push-button causes the lead chamber to advance, thereby causing the lead to advance. The lead chamber is in an incrementally slide-able relationship to the barrel, such that the lead chamber is allowed to advance in a predetermined increment. Therefore, advancement of the lead is limited to the incremental movement of the lead chamber. As was the case with side-knock pencils, the lead in push-button pencils can only be advanced in predetermined increments.
Rotary-knock mechanical pencils include both forward and rearward outer cylinders. A cam-movement converting mechanism is stored in the forward cylinder to convert rotary movement of the rearward cylinder into an axial advancing movement. By rotating the rearward cylinder, lead is advanced forward to extend beyond the forward cylinder, thereby allowing a user to selectively advance and use the lead. While such mechanisms are not limited to the incremental advancement of the lead, they include multiple and complex parts which may be prone to breakage.
Thus, a continuing need exists for a mechanical pencil that relies on a simple mechanism to smoothly advance the lead without the incremental advancement mechanisms found in the prior art.